DESCRIPTION: The atomic resolution structures of viruses provide a new framework for studying the interaction of viruses with their cellular receptors, designing anti-viral therapeutics, and understanding the bonding interactions in complex macromolecular assemblies. Although these structures represent well-resolved end-products, the process of virus assembly remains ill-defined with regard to its regulation within virus-infected cells and the properties of the viral structural proteins which determine the pathways of assembly. The study of virus assembly has direct implications for designing anti-viral therapies, but also has relevance to the general biologic problems of protein folding, protein trafficking within cells, and the interaction of eukaryotic chromosomes with structural proteins. The aims of this proposal are directed at understanding the structure and assembly of papovaviruses at the atomic, biochemical, and cell biological levels. A structural analysis of the human papillomavirus (HPV) subtype-11 L1 capsid protein will be undertaken using a recombinant L1 protein as a substrate for interactions between the papovavirus "minor" capsid proteins and the capsid will be studied using cryoelectron microscopy of virus-like particles purified after expression of polyoma capsid proteins in insect cells, and biochemical characterization of polyomavirus VP1/VP2/VP3 or HPV L1/L2 complexes. Using mutant polyoma VP1 proteins subdomains of the VP1 carboxy terminus will be analyzed in relation to their effect upon the size, shape, and curvature of capsids formed in vitro. The interaction of polyoma VP1 with cell chaperone proteins will be analyzed to determine whether chaperone binding influences association of VP1 capsomeres into capsids. The in vivo effects of calcium, protein concentration, and chaperone binding on capsid assembly will be tested using mutant VP1 proteins expressed in insect cells.